1. Field of the Invention
The invention relates to a combination bottle finish and closure having slots for the venting of the container head space during removal of the closure.
2. Description of the Prior Art
Twist-off molded thermoplastic closures are becoming increasingly important in the bottling industry. A problem with twist-off closures sealing containers of pressurized fluids is the possibility of the premature release of the closure during removal. During rotational removal of the closure, the seal between the closure and finish is broken, allowing head space pressure to be applied to the closure skirt. The pressure may be sufficient to overcome the limited remaining thread engagement between the closure and finish, causing the closure to be violently propelled from the finish. Attempts have been made to alleviate this hazard by the provision of venting means on the closure or finish.
For example, U.S. Pat. No. 4,007,848, to Snyder, discloses a glass bottle finish having axial slots formed through the threaded portion of the finish. U.S. Pat. No. 4,007,851, to Walker, discloses an aluminum twist off closure for containers of carbonated beverages having radially extending venting apertures formed through the skirt thereof.
The prior art also includes closures providing safety venting means for the release of excessive fluid pressure occurring at any time, not only during rotational removal of a threaded closure. Such prior art is typified by U.S. Pat. No. 2,990,079 to Garvey.